# A Nuclear Reaction: Determining the velocity of neutrons

## Homework Statement

Fission, the process that supplies energy in nuclear power plants, occurs when a heavy nucleus is split into two medium-sized nuclei. One such reaction occurs when a neutron colliding with a 235U (uranium) nucleus splits that nucleus into a 141Ba (barium) nucleus and a 92Kr (krypton) nucleus. In this reaction, two neutrons also are split off from the original 235U. Before the collision, the arrangement is as shown in the figure (a). After the collision, the 141Ba nucleus is moving in the +z - direction and the 92Kr nucleus in the −z - direction. The three neutrons are moving in the xy-plane, as shown in the figure (b) (Figure 1) .[/B]

If the incoming neutron has an initial velocity of magnitude 3.0×10^3m/s and a final velocity of magnitude 2.0×10^3m/s in the directions shown, what are the speeds of the other two neutrons? (The mass of the 141Ba nucleus is approximately 2.3×10^−25kg, and the mass of 92Kr is about 1.5×10^−25kg.)

Pi_x=Pf_x

Pi_y=Pf_y

## The Attempt at a Solution

I have tried this problem several different ways and keep getting stuck. I have been told my approach is correct, however there are some errors present. Can someone please help me through this problem. Thank you [/B]

#### Attachments

TSny
Homework Helper
Gold Member
Hello. Welcome to PF.

Your work looks good to me. How do you know there are errors present? Your final answer for Vn1 has been rounded to only one significant figure.

• maxd23
Hello. Welcome to PF.

Your work looks good to me. How do you know there are errors present? Your final answer for Vn1 has been rounded to only one significant figure.
T

here was a rounding error, the final answer is 220 m/s and 1000 m/s

Thanks

TSny
Homework Helper
Gold Member
OK. Good work!

• maxd23